Photolithography is a process of transferring geometric shapes on a mask to the surface of a silicon wafer or substrate of a liquid crystal display. Typically, the steps involved in the photolithographic process are: wafer cleaning; barrier layer formation; photoresist application; soft baking; mask alignment; exposure and development; and hard baking. Photoresist application is an important step during photolithography.
FIG. 6 shows a conventional photoresist coating apparatus. The coating apparatus 10 includes a work table 16, a photoresist coating nozzle 11, a supplying device 12 for supplying photoresist, a slot 15 for cleaning of the nozzle 11, and two guide rails 17 disposed on two opposite sides of the work table 16. Two opposite ends of the nozzle 11 are respectively connected to the guide rails 17. The nozzle 11 is connected to the supplying device 12. An LCD substrate 13 to be coated is fixed on the work table 16.
Referring to FIG. 7, in operation, the supplying device 12 supplies photoresist 14 to the nozzle 11, the nozzle 11 progressively slides along the guide rails 17 from point A to point B, and the photoresist is progressively coated on the substrate 13 as a continuous layer by the nozzle 11. After coating, the nozzle 11 should be dipped into the slot 15 for cleaning.
However, there are some difficulties that can arise in the coating process using the coating apparatus 10. There may be some foreign particles on the surface of the work table 16 or on the backside of the substrate 13, due to unclean working conditions. Static electricity may be produced between the substrate 13 and the work table 16. The foreign particles and the static electricity may result in imperfections in the coating process.
What is needed, therefore, is a coating apparatus and a coating method that can help to overcomes these difficulties.